Loud-speaking device



March 27, 1928. 1,664,017

J. C. BENJAMIN LOUD SPEAKING DEVICE Filed Nov. 4. 1924 generally known as Patented Mar. 27, 1928.

UNITED STATES PATENT OFFICE.

JOHN C. BENJAMIN, OF BRONXVILLE, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

LOUD-SPEAKING DEVICE.

Application filed November 4, 1924. Serial No. 747,735.

This invention relates to an acoustic apparatus, the object being to provide an acoustic device capable of accurately respending to and reproducing vibrations within the audible range, and in which the amount of distortional interference is reduced to a minimum.-

Heretofore the acoustic devices of that type which comprised conical shaped fibre, or paper, diaphragms, particularly those consisting of two diaphragms having their bases peripherally fastened together, were arranged with the apexes of the cones indistant relation to each other. In this arrangement the magnetic actuating means, the receiver element, is subject to considerable unbalance due to the expansion and contraction of the materials in the diaphragm s, which seriously affects the accurate response of the receiver element to currents representing frequencies within the voice and musical range.

This objection is overcome in the present invention by so arranging the diaphragms that any expansion or contraction in one provides for an equal and opposite amount in the other, thereby neutralizing any unbalance due to thermal or humidity changes in the above mentioned diaphragms.

There is also provided by this inventionan air chamber between the two diaphragms whose volume in comparison to those pro vided in similar devices, heretofore disclosed, is greatly reduced. This provision is particularly advantageous inasmuch as it reduces the low frequency characteristic peak by dampening the vibrations of thediaphragms and producing thereby a higher quality ot reproduction.

Another feature of the invention is to produce a directional effect in the projection of the sound by concentrating most of the sound waves on the concave side of the device.

In the drawing, Fig. 1 is a side elevation and a partial sectional view of the device embodying the invention.

Fig. 2 is a front view of the device shown in Fig. 1.

Fig. 3 is a side elevation and partial sectional View showing the modification of Fig. 1.-

In the preferred form of the device, shown in Fig. 1, a standard 10 carries at its upper cated conical diaphragm, conical diaphragm end and integrally formed therewith an arm 11 on WlllCh is supported a magnetic actuatmg means 12. The actuating means 12 is located withln a truncated conical shaped d aphragm 13 which is supported by an upright annular member 14, also formed. integrally with the standard 10. This actuatmg means may be of any well known type of receiving magnetic systems but it is preferable to use one of the types described in Patent No. 1,365,898, of January 18, 1921, to H. C. Edgerton. serves as a reenforcing means for the conical shaped diaphragm 15 to which it is peripherally secured, and the diaphragm 15 having a fiatter slope than that of the truncated diaphragm is invertedly arranged or nested in the dlaphragm 13. The apex of the diaphragm 15 is connected to the actuating meansby a rod 16 which serves to transmit v bratlons from the actuating means to the diaphragm or vice versa.

In this invention diaphragms 13 and 15 are sub ect to the same temperature and humidity condition-s and are made of such material that their expansion and contractlon are approximately the same. Due to their position the expansion which occurs 1n diaphragm 13 actuates outwardly and is approximately equal to the expansion of dlaphragm 15 which actuates inwardly. This means that the relative position of the apex of diaphragm 15 remains unchanged during temperature and humidity changes and that therefore the balance of the armature in the receiver element is maintained.

In the modified form of the invention, shown in Fig. 3, the positions of the diaphragms 20and 21 are reversed to those shown in Fig. 1, the truncated diaphragm 21 being nested in the full diaphragm 20.

What is claimed is:

1. An acoustic device comprising a plurality of coaxially arranged diaphragnis one disposed within another, peripherally secured together and arranged to provide therebetween an air chamber, and actuating means for said diaphragms located in said chamber.

2. An acoustic device comprising a truna direct-acting full arranged within and joined to said truncated diaphragm to form a chamber therebetween, and an actuating The diaphragm 13 also 7 mechanism within said chamber connected with said direct-acting diaphragm and pro videdt'or converting electrical energy into sound energy.

3. An acoustic device comprising a truncated conoidally formed diaphragm, a direct-actin'g full conoidally formed diaphragm nested within and secured to said phragms out various slopes, one disposedwithin another and peripherally secured thereto, the arrangement of said dlaphragms providing therein an air chamber, and actuating means for said diaphragms within said chamber, and a rod connecting one out said diaphragms with said actuating means, said arrangement of the diaphragms being nee'aoi'r provided to maintain a constant balance in said actuating means.

5. An acoustic device comprising two one with the flatter slope being arranged Within the other and both being peripherally fastened together providing therebetween an air chamber, and a magnetic actuating means within said chamber, said arrangement of diaphragms being provided to concentrate most of the vibrations due to the operation of said actuating means on one side oi the device. I

6. An acoustic device comprising a plurality ot conical members having their apices spaced apart and pointing in the same direction, secured together to form an air chamber, and actuating means Within said chamber connected to one of said members.

In Witness whereof, I hereunto subscribe my name this 3rd day of November, A. D. 192d.

JOHN G. BENJAMIN. 

